Node.js

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    //  This example assumes the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    var fac = new chilkat.FileAccess();
    var compress = new chilkat.Compression();
    compress.Algorithm = "deflate";

    var streamC = new chilkat.Stream();

    //  This example sets the source and sink of the stream to files.
    //  A stream can have use other streams as a source or sink,
    //  or the application can itself be the source/sink by directly
    //  reading or writing a stream.  (See below for an example of this..)
    streamC.SourceFile = "qa_data/hamlet.xml";
    streamC.SinkFile = "qa_output/hamlet_compressed.dat";

    //  Compress from source to sink.
    success = compress.CompressStream(streamC);
    if (success !== true) {
        console.log(compress.LastErrorText);
        return;
    }

    console.log("File-to-file deflate compression successful.");
    //  Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    //  the size of the file as a string, then convert to an integer value.
    console.log("Original size = " + fac.FileSize(streamC.SourceFile));
    console.log("Compressed size = " + fac.FileSize(streamC.SinkFile));

    //  Now do file-to-file decompression
    var streamD = new chilkat.Stream();
    streamD.SourceFile = "qa_output/hamlet_compressed.dat";
    streamD.SinkFile = "qa_output/hamlet_restored.xml";

    //  Decompress from source to sink.
    success = compress.DecompressStream(streamD);
    if (success !== true) {
        console.log(compress.LastErrorText);
        return;
    }

    console.log("File-to-file deflate decompression successful.");

    //  Let's double-check to see that the files are equal in size and content:

    var bFilesEqual = fac.FileContentsEqual(streamC.SourceFile,streamD.SinkFile);
    if (bFilesEqual !== true) {
        console.log("The output file is not equal to the input file!");
    }
    else {
        console.log("The file was successfully compressed and decompressed.");
    }

    //  ---------------------------------------------------------------------
    //  Now let's decompress again, but this time w/ the application reading
    //  the decompressed data directly from a stream.
    var streamA = new chilkat.Stream();

    streamA.SourceFile = "qa_output/hamlet_compressed.dat";

    //  Start decompressing in a background thread.
    // task: Task
    var task = compress.DecompressStreamAsync(streamA);
    success = task.Run();

    //  Read decompressed data from streamA:
    var decompressedText;
    while ((streamA.EndOfStream !== true)) {
        if (streamA.DataAvailable == true) {
            decompressedText = streamA.ReadString();
            console.log(decompressedText);
        }

    }

    //  Let's make sure the background task finished and that the decompress was successful.
    //  It should already be the case that the task is finished.
    while ((task.Finished !== true)) {
        task.SleepMs(20);
    }

    //  The decompressor may have finished, but it is possible that data
    //  remains to be flushed.  
    if (streamA.DataAvailable == true) {
        decompressedText = streamA.ReadString();
        console.log(decompressedText);
    }

    //  Did streamA succeed in reading the entire file?
    if (task.TaskSuccess !== true) {
        console.log("async decompress failed:");
        console.log(task.ResultErrorText);
        success = false;
    }

    console.log("The async decompress was successful.");

}

chilkatExample();